What is waterproofing? Waterproofing is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water. In other words, it helps an object with resisting the ingress of water under specified conditions. Waterproofing is important to many industries, but here we will discuss its relevance for fabrics, apparel & footwear.
When thinking about waterproofing in regard to garments, it is important to consider that waterproofing techniques can take place at the fabric or garment level (or steps taken regarding the fabric and steps taken when sewing the garments).
Waterproof fabrics are fabrics that are inherently, or have been treated to become, resistant to penetration by water and wetting.
The term "waterproof" refers to conformance to a governing specification and specific conditions of a laboratory test method. They are usually natural or synthetic fabrics that are laminated to or coated with a waterproofing material such as rubber, polyvinyl chloride (PVC), polyurethane (PU), silicone elastomer, fluoropolymers, and wax. Treatment could be either of the fabric during manufacture or of completed products after manufacture, for instance by a waterproofing spray. Examples include the rubberized fabric used in Mackintosh jackets or sauna suits.
Waterproof/breathable fabrics resist liquid water passing through, but allow water vapour to pass through. Their ability to block out rain and snow while allowing vapour from sweat to evaporate leads to their use in rainwear, waterproof outdoor sports clothing, tents, and other applications.
Why do we need waterproof textiles? Go outside in the rain without an umbrella and you may better understand the need for waterproofing.
Typical descriptions are "showerproof", "water resistant", and "waterproof".
Waterproof garments specify their hydrostatic rating, ranging from 1,500 for light rain, to 20,000 for heavy rain. Waterproof garments are intended for use in weather conditions which are often windy as well as wet, and are often also wind resistant.
Methods of making fabric water resistant:
Durable water repellent, or DWR , is a coating added to fabrics at the factory to make them water-resistant (hydrophobic).
Most factory-applied treatments are fluoropolymer based; these applications are quite thin and not always effective. Durable water repellents are commonly used in conjunction with waterproof breathable fabrics such as Gore-Tex to prevent the outer layer of fabric from becoming saturated with water. This saturation, called 'wetting out,' can reduce the garment's breathability (moisture transport through the breathable membrane) and let water through. As the DWR wears off over time, re-treatment is recommended when necessary. Many spray-on and wash-in products for treatment of non-waterproof garments and re-treatment of proofed garments losing their water-repellency are available from sources of sporting apparel. Older methods for factory application of DWR treatments involve applying a solution of a chemical onto the surface of the fabric by spraying or dipping.
Some researchers have suggested that the use of PFAS's in water-repellent clothing is over-engineering, and comparable performance can be achieved using specific silicon- and hydrocarbon-based finishes.
You might want to also learn about lanolin which is extracted from wool.